Rendering smoke and volume object which is emitting light causes black spots
It looks like i've solved my problem. I've changed muzzle flash volume object that was appearing and disappearing - now it's a paricle emitter. Particle lifetime is just one frame so it looks pretty similar to previous effect. Smoke is not hidden anymore because there is no object that could do this - particle emitter surface is not visible and muzzle flash particle is there for very short time. 

Strange thing is (which I've not expected when i was thinking about this solution)  that particle - which is an object with volume shader - is not bugging anymore! I mean there is no black deformations inside flash object even when all objects are on the same render-layer.

This funny trick fixed my problem but it will probably still exist if someone try to render smoke and volume object inside which is not moving or disappearing - black deformations on volume and hidden smoke when volume density is set at 0.000.



I hope this will help somebody.